Mandrel segment loader

ABSTRACT

A mandrel segment loader provides a reliable means of assembling the segments of a large multi-piece mandrel designed for the lay-up of composite materials in the manufacture of large structures such as one-piece fuselage barrels for wide-body aircraft and can also be used for removing the mandrel from the finished fuselage barrel by disassembling the segments. The mandrel segment loader provides transport and multi-axis positioning for the segments, which may weigh as much as 25,000 pounds, with linear positioning resolution in the realm of 0.002 inch and rotational positioning resolution in the realm of 0.005 degree. The mandrel segment loader is also more generally useful as a material handling system that can perform many useful manufacturing functions, such as loading passenger floors into a fuselage barrel when assembling an aircraft. Self-locking grippers prevent accidental self-release of a load.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is related to the following co-pending UnitedStates patent applications: U.S. application Ser. No. 10/851,381, filedMay 20, 2004; U.S. application Ser. No. 10/822,538, filed Apr. 12, 2004;U.S. application Ser. No. 10/717,030, filed Nov. 18, 2003; U.S.application Ser. No. 10/646,509, filed Aug. 22, 2003; U.S. applicationSer. No. 10/646,392, filed Aug. 22, 2003; U.S. application Ser. No.10/646,316, filed Aug. 22, 2003; U.S. application Ser. No. 10/630,594,filed Jul. 28, 2003; and U.S. application Ser. No. 10/301,949, filedNov. 22, 2002.

BACKGROUND OF THE INVENTION

The present invention generally relates to manufacturing of largestructures using composite materials and, more particularly, to a large,mobile robotic arm for manipulation of the mandrels used for laying upcomposite laminate material for the manufacture of large aircraftfuselage sections.

The structural performance advantages of composites, such as carbonfiber epoxy and graphite bismaleimide (BMI) materials, are widely knownin the aerospace industry. Aircraft designers have been attracted tocomposites, for example, because of their superior stiffness, strength,and lower weight. As more advanced materials and a wider variety ofmaterial forms have become available, aerospace usage of composites hasincreased. Composite materials have been applied using contour tapelaminating machines (CTLM) and automated fiber placement machines(AFPM), for example, in the manufacture of parts such as wing panels andempennage. New and innovative composite lamination technologies areenvisioned, such as the manufacture of large aircraft fuselage sectionsthat may exceed, for example, 15 to 20 feet in diameter. Newsuper-efficient aircraft—with the majority of the primary structure,including the fuselage and wing, made of composite materials—arecontemplated that, in addition to bringing big-jet ranges to mid-sizeairplanes, will provide airlines with unmatched fuel efficiency,resulting in exceptional environmental performance. It is expected thatsuch aircraft may use 20 percent less fuel for comparable missions thanany other current wide-body airplane yet be able to travel at speedssimilar to today's fastest wide-bodies, about Mach 0.85, and provide 40to 60 percent more cargo revenue capacity.

For the manufacturing of comparatively smaller parts, such as wingpanels and empennage, the CTLM and AFPM technologies have become highlydeveloped. Since composite materials have material characteristics thatdiffer from traditional aircraft materials, however, it will generallynot be possible to use existing facilities and equipment for theconstruction and assembly of the new, large, composite materialaircraft. For example, the large fuselage sections to be made out of acomposite material, and which can be described as having a one-piecebarrel shape, could be approximately 24 feet long with a diameter ofabout 20 feet and, therefore, quite large. This large fuselage barrel isa one-piece composite part that could be built by being laid up on alarge, multi-piece mandrel whose outer surface is the inner mold line(IML) of the aircraft fuselage. The multi-piece mandrel must beassembled from segments prior to lay-up and disassembled after partcure, i.e., after curing of the composite material, such as agraphite/epoxy, the inner mold line mandrel needs to be removed. Amethod and equipment will be required for assembling and disassemblingthe large, heavy mandrel segments.

SUMMARY OF THE INVENTION

A mandrel segment loader provides a reliable means of assembling thesegments of a large multi-piece mandrel between the rings of a fixedring assembly and disassembly station (FRADS). The multi-piece mandrel,for example, may be an inner mold line mandrel specifically designed forthe lay-up of composite materials in the manufacture of large structuressuch as one-piece fuselage barrels for wide-body aircraft. The mandrelsegment loader can also be used to pull the mandrel segments out againfrom the center of the finished fuselage barrel, by disassembling thesegments from between the rings of the FRADS. The mandrel segment loadercan also be used to transport mandrel segments, e.g., between differentworkstations on the factory floor.

In one embodiment of the present invention, a material handling systemincludes an arm that rotates about an A-axis. The arm has a Z₁-axis infixed relation to the arm and perpendicular to the A-axis, and has aZ₂-axis in fixed relation to the arm and parallel to the Z₁-axis so thatthe Z₁-axis and Z₂-axis rotate together about the A-axis. The systemalso includes a bridge carried by the arm. The bridge has a Y₁-axismaintained perpendicular to the Z₁-axis and a Y₂-axis maintainedperpendicular to the Z₂-axis. The bridge also has an X₁-axis maintainedperpendicular to the Y₂-axis.

The bridge translates relative to the arm along the Z₁-axis and Z₂-axisindependently and translates relative to the arm along the Y₁-axis andY₂-axis independently. A first gripper and a second gripper are providedfor gripping the material. The first gripper and second gripper arecarried by the bridge and translate along the X₁-axis of the bridge. Thefirst gripper and the second gripper are translated along the Z₁-axisand Z₂-axis differentially to produce rotation about a virtual B-axisperpendicular to the Z₁-axis and Z₂-axis. In addition, the first gripperand the second gripper are translated along the Y₁-axis and Y₂-axisdifferentially to produce rotation about a virtual C-axis perpendicularto the Y₁-axis and Y₂-axis.

In another embodiment of the present invention, a gripper includes amain pivot; a thumb for engaging a bar attached to a load, and a fingerfor engaging the bar attached to the load. The thumb pivots about themain pivot and has a thumb pivot connecting to a thumb control link. Thefinger pivots about the main pivot in opposition to the thumb and has afinger pivot connecting to a finger control link. An actuator rod has anactuator pivot connected to the thumb control link that is connected tothe thumb pivot. The actuator pivot is also connected to the fingercontrol link that is connected to the finger pivot.

Movement of the actuator rod in a first direction transmits forcethrough the thumb control link and finger control link to close thethumb and finger for engaging the bar attached to the load. Counterforce tending to open the finger and thumb is transmitted back throughthe thumb control link and finger control link to push the actuator rodin the first direction closing the thumb and finger to provide theself-locking characteristic of the gripper.

In still another embodiment of the present invention, a mandrel segmentloader includes a bridge that translates relative to an arm in thedirections of a Z₁-axis, a Y₁-axis, a Z₂-axis, and a Y₂-axis allindependently of each other. The Z₁-axis and Y₁-axis are perpendicular,and the Z₂-axis and Y₂-axis are perpendicular. The Z₁-axis and Z₂-axisare parallel and maintained in fixed relation to each other and the arm.Coordinated motion of the bridge in the directions of the Y₁-axis andthe Y₂-axis provides rotation about a C-axis that is a virtual axisperpendicular to the Y₁-axis and Y₂-axis. Coordinated motion of thebridge in the directions of the Z₁-axis and the Z₂-axis providesrotation about a B-axis that is a virtual axis perpendicular to theZ₁-axis and Z₂-axis. A self-locking gripper translates relative to thebridge in the direction of an X₁-axis relative to the bridge and rotatesabout an A′-axis relative to the bridge.

In a further embodiment of the present invention, a method of materialhandling includes the operations of: gripping the material using a firstgripper and a second gripper; carrying the first gripper and secondgripper on a bridge having a Y₁-axis maintained perpendicular to aZ₁-axis and a Y₂-axis maintained perpendicular to a Z₂-axis, the bridgealso having an X₁-axis maintained perpendicular to the Y₂-axis; androtating the bridge about an A-axis on an arm, the arm having theZ₁-axis in fixed relation to the arm and perpendicular to the A-axis,and having the Z₂-axis in fixed relation to the arm and parallel to theZ₁-axis so that the Z₁-axis and Z₂-axis rotate together about theA-axis. The method also includes the operations of: translating thebridge relative to the arm along the Z₁-axis and Z₂-axis independentlyand translating the bridge relative to the arm along the Y₁-axis andY₂-axis independently; translating the first gripper and the secondgrippers together along the X₁-axis; translating the first gripper andthe second gripper along the Z₁-axis and the Z₂-axis differentially toproduce rotation about a virtual B-axis perpendicular to the Z₁-axis andZ₂-axis; and translating the first gripper and the second gripper alongthe Y₁-axis and the Y₂-axis differentially to produce rotation about avirtual C-axis perpendicular to the Y₁-axis and Y₂-axis.

In a still further embodiment of the present invention, a method ofassembling aircraft includes the steps of: gripping a mandrel segment;and accurately positioning the mandrel segment relative to a ring of afixed ring assembly and disassembly station.

These and other features, aspects and advantages of the presentinvention will become better understood with reference to the followingdrawings, description and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a material handling system in accordancewith one embodiment of the present invention.

FIG. 2 is a perspective view from a different angle of the materialhandling system shown in FIG. 1.

FIG. 2A is a perspective view of a mandrel segment loader positioning amandrel segment between rings of a fixed ring assembly and disassemblystation (FRADS) according to one embodiment of the present invention.

FIG. 2B is a perspective view of a mandrel segment loader insertedbetween three mandrel segments attached between rings of a fixed ringassembly and disassembly station (FRADS) according to one embodiment ofthe present invention.

FIG. 3 is a perspective view of a mast of the material handling systemshown in FIG. 1.

FIG. 4 is a perspective view of a lift truck carriage assembly of thematerial handling system shown in FIG. 1.

FIG. 5 is a perspective view of an arm of the material handling systemshown in FIG. 1.

FIG. 6 is a perspective view of a bridge and arm assembly of thematerial handling system shown in FIG. 1.

FIG. 7 is a front perspective view of the fore part of the bridge,showing front grippers, of the material handling system shown in FIG. 1.

FIG. 8 is a rear perspective view of the fore part of the bridge of thematerial handling system shown in FIG. 1.

FIG. 9 is a top perspective view of the fore part of the bridge of thematerial handling system shown in FIG. 1.

FIG. 10 is a perspective view of a portion of the bridge assembly,showing rear grippers, of the material handling system shown in FIG. 1.

FIG. 11A is a perspective view of a gripper of the material handlingsystem shown in FIG. 1.

FIG. 11B is a top view of a gripper of the material handling systemshown in FIG. 1.

FIG. 11C is a side view of a gripper of the material handling systemshown in FIG. 1.

FIG. 11D is a cut away view of a gripper of the material handling systemshown in FIG. 1.

FIG. 11E is a cross sectional view taken generally along line 11E-11E ofFIG. 11D.

FIG. 12A is a side view of an actuator of the material handling systemshown in FIG. 1.

FIG. 12B is a cross sectional view of an actuator taken generally alongline 12B-12B of FIG. 12A.

DETAILED DESCRIPTION OF THE INVENTION

The following detailed description is of the best currently contemplatedmodes of carrying out the invention. The description is not to be takenin a limiting sense, but is made merely for the purpose of illustratingthe general principles of the invention, since the scope of theinvention is best defined by the appended claims.

The Boeing Company is exploring a variety of methods and tools formaking large composite structures. The present application describes aninvention that is one of a family of inventions for accomplishing thisgoal. The present application is related to the following co-pendingUnited States patent applications that are part of this family: U.S.application Ser. No. 10/851,381, filed May 20, 2004, entitled “CompositeBarrel Sections for Aircraft Fuselages and Other Structures, and Methodsand Systems for Manufacturing such Barrel Sections”; U.S. applicationSer. No. 10/822,538, filed Apr. 12, 2004, entitled “Systems and Methodsfor Using Light to Indicate Defect Locations on a Composite Structure”;U.S. application Ser. No. 10/717,030, filed Nov. 18, 2003, entitled“Method of Transferring Large Uncured Composite Laminates”; U.S. patentapplication Ser. No. 10/646,509, entitled “Multiple Head AutomatedComposite Laminating Machine For The Fabrication Of Large Barrel SectionComponents”, filed Aug. 22, 2003; U.S. patent application Ser. No.10/646,392, entitled “Automated Composite Lay-Up To An Internal FuselageMandrel”, filed Aug. 22, 2003; U.S. patent application Ser. No.10/646,316, entitled “Unidirectional, Multi-Head Fiber Placement”, filedAug. 22, 2003; U.S. patent application Ser. No. 10/630,594, entitled“Composite Fuselage Machine”, filed Jul. 28, 2003; and U.S. patentapplication Ser. No. 10/301,949, entitled “Parallel ConfigurationComposite Material Fabricator”, filed Nov. 22, 2002; which areincorporated by reference.

Broadly, the present invention provides innovative methods and equipmentfor the construction and assembly of large aircraft from compositematerials—such as large, one-piece, composite fuselage barrels that mayapproach or exceed 20 feet in maximum cross section (“diameter”) and 24feet in length. Embodiments of the present invention provide methods andequipment for assembling and disassembling large, heavy mandrel segmentsof a multi-piece mandrel used for the lay-up of large composite parts.Such a large, multi-piece mandrel, for example, may have an outer lay-upsurface that is the inner mold line (IML) of the fuselage for awide-body aircraft and the segments may be assembled between the ringsof a fixed ring assembly and disassembly station (FRADS). The materialhandling system of one embodiment may be realized by a mandrel segmentloader that can also be used to transport mandrel segments, for example,between different workstations on the factory floor. In addition, thematerial handling system of one embodiment can be used in a transportand assembly/disassembly mode for other purposes such as loadingpassenger floor structures into the fuselage barrel when assembling anaircraft. The material handling system of one embodiment also can beused in a manlift mode, for example—along with scaffolding that may beattachable to a gripper interface—to allow a mechanic access to themandrel segments during assembly and disassembly. The material handlingsystem of one embodiment can also be used in a mandrel segmentpreparation mode, for example, to allow a mechanic to clean and applyrelease agent to the mandrel segment in an ergonomic orientation.

Using the mandrel segment loader of one embodiment, the inner mold line,multi-piece mandrel can be assembled prior to lay-up of a fuselagebarrel built by being laid up on the large, multi-piece mandrel. Themandrel can be removed from the fuselage barrel after part cure, i.e.,after curing of the composite material, such as a graphite/epoxy, bydisassembling the multi-piece mandrel while using the mandrel segmentloader to support and remove the segments from the inside of the curedcomposite fuselage barrel as each segment is disassembled from themandrel and from between the rings of the FRADS.

One embodiment is a novel mobile material handling system that cantransport mandrel segments, rotate around any point on the factoryfloor, crab sideways, or move at any angle. The material handling systemof one embodiment includes seven axes of motion that allow a mandrelsegment loader to position mandrel segments accurately between the ringsof the FRADS with the degree of accuracy required for reliable assembly(and disassembly) of the mandrel and in a wide array and combination ofmovements that is novel in the art of manipulating large heavy objects.A mandrel segment may have a width, for example, of about 10 feet, alength of about 25 feet up to 28 feet, and may weigh in the neighborhoodof 10,000 pounds. The material handling system of one embodiment, forexample, can manipulate and position loads in a range from any load thatis not too small to be provided with a gripper interface (e.g., 100pounds) up to loads of approximately 25,000 pounds with linearpositioning resolution in the range of 0.002 to 0.005 inch and angularpositioning resolution in the range of 0.005 to 0.01 degrees.

Referring now to the figures, FIG. 1 illustrates a material handlingsystem incorporating mandrel segment loader 100 according to oneembodiment. Mandrel segment loader 100 may include chassis 102 thatsupports the remainder of mandrel segment loader 100 and provides formovement of loader 100, for example, over a shop or factory floor.Chassis 102 may be provided with wheel units and a control system (notshown)—such as those manufactured by MaxMove AB of Bjurholm, Sweden—thatprovide translation in the direction of X-axis 104 and in the directionof Y-axis 106, which may be horizontal, in any combinationsimultaneously so that chassis 102 can, for example, crab sideways ormove at any angle relative to X-axis 104 and Y-axis 106. More generally,chassis 102 can move across a floor in any direction chosen by anoperator, including up a 2.5% maximum grade or down a grade and canperform a C′-axis 108 rotation (rotation about an axis that isperpendicular to both X-axis 104 and Y-axis 106) centered at any chosenpoint, for example, on the floor supporting chassis 102. Chassis 102 mayhave an overall length of approximately 34 feet and overall width ofapproximately 17 feet, and mandrel segment loader 100 may have onoverall height of approximately 22 feet with a maximum height of about28 feet when positioned as seen in FIG. 2. Mandrel segment loader 100may, for example, be capable of positioning a maximum load of 10,000pounds with the degree of accuracy described. Human figures 110 shown inFIGS. 1 and 2 provide an indication of the relative size of mandrelsegment loader 100 for transporting a mandrel segment.

FIG. 2A shows a mandrel segment loader 100 with arm 128 rotated aboutA-axis 130 and holding a mandrel segment 101 in position between rings302 and 304 of a fixed ring assembly and disassembly station (FRADS)300. FIG. 2A also shows the position of chassis 102 relative to rings302 and 304 when positioning a mandrel segment. The Z₁-actuator 140 andZ₂-actuator 142, rotated about A-axis 130, may also be more clearly seenin this figure. FIG. 2B shows a mandrel segment loader arm and bridge160 in position between three mandrel segments 101 after the mandrelsegments 101 have been positioned by mandrel segment loader 100 andaffixed to rings 302 and 304, for example, by bolts. Grippers 196 may beseen at the front of bridge 160 as well as a number of the bars 103attached to mandrel segments 101 and used by mandrel segment loader 100to grip each mandrel segment 101 using grippers 196.

Mandrel segment loader 100 may include a mast 112, as shown in FIGS. 1and 2 and more clearly seen in FIG. 3. Mast 112 may have nested,interlocking I-beam sections 114 made of rolled carbon steel with crossbracing 116 to guarantee maximum strength, rigidity and stability with afull load at maximum height, to prevent breakage and distortion due tobending. Mast 112 may be attached to chassis 102 and may be furthersupported by guys 118. Lift truck carriage 120, shown in FIGS. 1 and 2and more clearly seen in FIG. 4, may be carried by mast 112 so that lifttruck carriage 120 can slide vertically up and down along mast 112,providing translation in the direction of W-axis 122 (see FIG. 1) of aload—such as a mandrel segment or passenger floor—gripped by mandrelsegment loader 100. For example, lift truck carriage 120 may be mountedto mast tracks 124 of mast 112 via load roller bearings and lateralthrust rollers 126. Load roller bearings and lateral thrust rollers 126may be permanently lubricated and mounted on trunnions to reducemaintenance and friction. Lateral thrust rollers 126 with shim or boltroller adjustment may be used to compensate for off-center loadingbetween lift truck carriage 120 and mast 112. W-axis 122 lift (e.g. forsliding lift truck carriage 120 along mast 112) may be hydraulicallyactuated, for example, or may be provided by a ball screw mechanism. TheW axis 122 lift of lift truck carriage 120 along mast 112 may beprovided at a rate of 0.0 to 2.0 inches per second, with a positioningaccuracy of 0.20 inch.

Arm 128, shown in FIGS. 1 and 2 and more clearly seen in FIG. 5, may bemounted on lift truck carriage 120 so that arm 128 may provide arotation about A-axis 130 (see FIG. 1) of a load—such as a mandrelsegment or passenger floor—gripped by mandrel segment loader 100. A-axis130, for example, may be horizontal and perpendicular to W-axis 122,which may be vertical. Mechanical power for rotating arm 128—and agripped load such as a mandrel segment or passenger floor—about A-axis130 may be provided by electric motors 132 mounted on lift truckcarriage 120. Motors 132, as well as any other motors used for mandrelsegment loader 100, should have sufficient horsepower and torque toinsure smooth operation of the material handling system, e.g., mandrelsegment loader 100, under all normal conditions. Drive motors and liftmotors should be separate. An A-axis 130 rotation may rotate a load from0 degrees to +/−190 degrees and may position the load within +/−0.5degree. The ability to turn more than halfway around may providepositioning flexibility, for example, in the range of +170 to +190degrees without having to rotate a load through 360 degrees to pick upall parts of that range. A-axis rotation speeds may be from 0 to 3degrees per second. As shown in FIG. 5, arm 128 may include a mountinginterface 134 allowing lift truck carriage 120 to support and rotate arm128 along with a gripped load and all system components carried by arm128. Arm 128 may include a truss structure 136 designed to support thearm 128, gripped load, and system components at any angle of rotationabout A-axis 130.

As shown in FIG. 6, actuators 138 are attached to arm 128. Actuators 138may include a Z₁-actuator 140 and a Z₂-actuator 142. The Z₁-actuator 140may provide translation relative to arm 128 of a load gripped by mandrelsegment loader 100 in the direction of the Z₁-axis 144 (see FIG. 1). TheZ₂-actuator 142 may provide translation relative to arm 128 of a load inthe direction of the Z₂-axis 146 (see FIG. 1). Actuators 138 may beelectrically or hydraulically actuated and may be moved and positionedindependently of one another. A control system (not shown) may beprovided so that motion in the direction of the Z₁-axis 144 can becoordinated with motion in the direction of the Z₂-axis 146. Forexample, if like motion is provided along both Z₁-axis 144 and Z₂-axis146, an overall Z-translation relative to arm 128 may be provided to aload, and if a differential motion is provided between Z₁-axis 144 andZ₂-axis 146, a rotation (in the plane of Z₁-axis 144 and Z₂-axis 146)about a B-axis 148 may be provided to a load, where the location of theB-axis 148, i.e., the center of rotation, is determined by the relativemotion along Z₁-axis 144 and Z₂-axis 146. Thus, B-axis 148 may be avirtual axis (perpendicular to the Z₁-axis 144 and the Z₂-axis 146) thatrotates using coordinated motion of the Z axes, Z₁-axis 144 and Z₂-axis146. The center of B-axis 148 rotation may be selectable by an operatorusing the control system, and the center of B-axis 148 rotation may belocated, for example, at each end of each mandrel segment.

Continuing with FIG. 6, Z₁-actuator 140 may carry a Y₁-actuator 150attached to Z₁-actuator 140 perpendicularly to the Z₁-axis 144 ofZ₁-actuator 140. Similarly, Z₂-actuator 142 may carry a Y₂-actuator 152attached to Z₂-actuator 142 perpendicularly to the Z₂-axis 146 ofZ₂-actuator 142. Y₁-actuator 150 may provide translation relative to arm128 of a load gripped by mandrel segment loader 100 in the direction ofthe Y₁-axis 154 (see FIG. 1). Y₂-actuator 152 may provide translationrelative to arm 128 of a load in the direction of the Y₂-axis 156 (seeFIG. 1). Actuators 150, 152, like actuators 138, may be electrically orhydraulically actuated and may be moved and positioned independently ofone another. The control system may be operated so that motion in thedirection of Y₁-axis 154 can be coordinated with motion in the directionof Y₂-axis 156. For example, if like motion is provided along both theY₁-axis 154 and the Y₂-axis 156, an overall Y-translation relative toarm 128 may be provided to a load, and if a differential motion isprovided between the Y₁-axis 154 and the Y₂-axis 156, a rotation (in theplane of the Y₁-axis 154 and the Y₂-axis 156) about a C-axis 158 may beprovided to a load, where the location of the C-axis 158, i.e., thecenter of rotation, is determined by the relative motion along theY₁-axis 154 and the Y₂-axis 156. Thus, the C-axis 158 may be a virtualaxis (perpendicular to the Y₁-axis 154 and the Y₂-axis 156) that rotatesusing coordinated motion of the Y axes, Y₁-axis 154 and Y₂-axis 156.Because the C-axis 158 is a virtual axis, the position of C-axis 158,i.e., center of rotation about C-axis 158, may be selectable by anoperator using the control system, and the center of rotation aboutC-axis 158 may be located, for example, so that each mandrel segment canbe rotated around each end of the mandrel segment and the center of themandrel segment.

The Y₁-actuator 150 and the Y₂-actuator 152 may carry a bridge 160attached to the Y₁-actuator 150 and the Y₂-actuator 152. Bridge 160 mayinclude a truss structure 162 designed to support—at any angle ofrotation about A-axis 130—the bridge 160 as well as a gripped load suchas a mandrel segment or passenger floor and all other system componentscarried by bridge 160. Because the Z₁-actuator 140 and the Z₂-actuator142 may be moved and positioned independently of one another, thedistance between the Y₁-actuator 150 and the Y₂-actuator 152 (e.g.,between the Y₁-axis 154 and the Y₂-axis 156) may change. Therefore, atleast one of the actuators 150 and 152 may be attached to bridge 160 viaa length adjustment mechanism 164 that compensates for changes indistance between the Y₁-axis 154 and the Y₂-axis 156 or between theY₁-actuator 150 and the Y₂-actuator 152. For example, the Y₁-actuator150 may be attached to a guide 166 that rides along a rail 168 attachedto bridge 160.

A load—such as a mandrel segment or passenger floor—may be translated inthe direction of X₁-axis 170 and X₂-axis 172, which may be collinearwith X₁-axis 170 or parallel to X₁-axis 170. In the example used here toillustrate one embodiment, the axes are collinear, i.e., identical, andtranslation may be described with respect to X₁-axis 170 only. Inalternative embodiments, the two axes could be parallel and translationscould be performed independently with respect to each axis. Translationof a load in the direction of X₁-axis 170 relative to bridge 160 may beachieved by moving cars 174 and 176 (see FIGS. 6 through 10) along guidetracks 178 and 180, respectively, that are attached to bridge 160. Cars174 and 176 ride on rollers that run within guide tracks 178 and 180 andmay be moved independently in an alternative embodiment. In the exampleused here to illustrate one embodiment, cars 174 and 176 may be linkedtogether to move in unison to keep cars 174 and 176 (and grippers 196)at the same relative distance from each other, which effectivelycombines X₁-axis 170 and X₂-axis 172 into a single X₁-axis 170.

Each of the X_(i), Y_(i), and Z_(i) axes (i=1,2) may be implementedusing servo-controlled positioning with travel speeds in the range of 0through 24 inches per minute and may have a positioning resolution inthe range of 0.002 to 0.005 inch. Total X_(i)-axis travel may beapproximately 8.0 inches, for example, total Y_(i)-axis travel may be inthe range of approximately +/−8.0 inches, and total Z_(i)-axis travelmay be approximately 25.0 inches.

Cars 174 and 176 may be supported by rollers on guide tracks 178 and 180in such a way that a rotation may be provided about A′-axis 194 (seeFIG. 1) relative to bridge 160 of a load—such as a mandrel segment orpassenger floor—gripped by mandrel segment loader 100. The rollers maybe lateral guide rollers, such as rollers 182, or load rollers thatprovide cars 174 and 176 support within the guide tracks 178 and 180 ina direction perpendicular to that of rollers 182. Either type of rollersmay be set on control shafts 184 on eccentrics to the longitudinalrotational axis 186 (see FIG. 9) of the shaft 184. Load rollerssupporting a car 174 (or 176) may be mounted on differential eccentricsas from one side 188 of the car 174 (or 176) to the opposite side 190 ofthe car 174 (or 176) (see, e.g., FIG. 9). Thus, coordinated rotation ofcontrol shafts 184 about their longitudinal rotational axes 186 using,for example, control levers 192 can be used to achieve a limited amountof rotation of the cars 174 and 176 relative to bridge 160 as, forexample, the eccentrics on one side 188 lower the car 174 (or 176) onthat side with respect to guide tracks 178 (or 180) and the eccentricson the opposite side 190 raise the car 174 (or 176) on that side withrespect to guide tracks 178 (or 180). By rotating both cars 174 and 176in unison, rotation of a load may be provided about A′-axis 194 relativeto bridge 160. An A′-axis 194 rotation may rotate a load in the range of+/−1 degree and may have a positioning resolution in the range of 0.005to 0.01 degree. An A′-axis 194 rotation may be considered as“fine-tuning” an A-axis 130 rotation, however, an A′-axis 194 rotationrotates a gripped load relative to bridge 160 (A′-axis 194 remainsparallel to X₁-axis 170 and X₂-axis 172) while an A-axis 130 rotationrotates a gripped load relative to arm 128 (A′-axis 194 may not remainparallel to A-axis 130 depending on motions of Z₁-axis 144, Z₂-axis 146,Y₁-axis 154, and Y₂-axis 156).

Interface of mandrel segment loader 100 to a load—such as a mandrelsegment or passenger floor—may be provided by grippers 196. For example,a pair of rear grippers 198 (see FIG. 10) are attached to and move withrear car 174. Front grippers 200 (see FIG. 8) attached to front car 176move so that grippers 196 (e.g., pairs of grippers 198 and 200) may bepositioned with respect to any combination of axes described above. Eachgripper 196 may grip a bar on the mandrel segment or other load to bemoved and positioned by the material handling system exemplified bymandrel segment loader 100. Grippers 196 may be operated, for example,electrically or pneumatically. Sensors—such as a limit switch orproximity switch—may be provided that indicate to the operator that aload such as a mandrel segment is being held securely by mandrel segmentloader 100.

To provide greater flexibility, for example, in the variety of loadscapable of being handled by mandrel segment loader 100, one or more ofthe grippers 196 may be “foldable” so that it can be moved out of theway into a folded position when not being used to grip a load. Gripper202, for example, is shown in a folded position in FIGS. 7 and 9 and isshown in an engaging position in FIG. 8. Foldable gripper 202 moves intransverse direction 272 (see FIG. 9) to provide additional flexibilityin positioning and configuration of grippers 196. Tab 274 on foldablegripper 202 may engage a notch 276, of which a multiple number may beprovided, in order, for example, to provide repeatable accuratepositioning and secure positioning when foldable gripper 202 is placedin the engaging position.

FIGS. 11A through 11E show additional details for a gripper 196. Gripper196 includes side guide plates 204 having a v-shaped notch that forms agripping guide 206 that may guide a bar attached to a load into agripping position 208 suitable for being held securely by gripper 196.Gripper 196 includes a thumb 210 and fingers 212 which may be opposableto each other and rotatable about main pivot 214 supported by side guideplates 204 so that thumb 210 and fingers 212 may open (as shown in FIG.11C) to release or accept a load and may close (as shown in FIGS. 11Aand 11D) to grip a load. Thumb 210 and fingers 212 may be actuated(electrically or pneumatically, for example) using actuator 216 to moveactuator rod 218 in the direction indicated by arrow 220 to close thumb210 and fingers 212 and in the direction indicated by arrow 222 to open.Actuator rod 218 may be connected via actuator pivot 224 to thumbcontrol link 226 and fingers control link 228. Actuator pivot 224 may beguided by guide slots 230 in side plates 232. Thumb control link 226 andfingers control link 228 may be connected in turn, respectively, viathumb pivot 234 and fingers pivot 236 to thumb 210 and fingers 212.Thus, movement and force may be transmitted from actuator rod 218 tothumb 210 and fingers 212. When in the closed position, as shown in FIG.11D, the center of actuator pivot 224 may be off line in the directionof arrow 220 from a line 238 passing through the centers of thumb pivot234 and fingers pivot 236. Any counter force tending to open thumb 210and fingers 212 from the vicinity of gripping position 208 applies acompressive moment to thumb pivot 234 and fingers pivot 236. The counterforce tends to push actuator pivot 224 (and actuator rod 218) further indirection of arrow 220, which is the direction for actuator rod 218 toclose thumb 210 and fingers 212, and firmly presses actuator pivot 224against the ends 240 of guide slots 230. Thus, grippers 196 in thisembodiment have a self-closing or self-locking property. Once a barattached to a load is engaged by a gripper 196, the load may be releasedonly by movement of actuator rod 218 in direction of arrow 222, which isthe direction for actuator rod 218 to open thumb 210 and fingers 212,and not by a counter force from the gripping position 208 forcing openthumb 210 and fingers 212.

FIGS. 12A and 12B show additional details for a ball screw actuator 242according to one embodiment, which may be used, for example, toimplement Z1-actuator 140, Z2-actuator 142, Y1-actuator 150, orY2-actuator 152. Outer sleeve 244, which is cylindrical, has a circularcross sectional bore to receive telescoping inner sleeve 246 and toallow rotation. The sleeves are sized to support the anticipated loadsand bending moments which may occur throughout the range of motion atany non-zero angle relative to the longitudinal axis 247 when a load ismoved. Outer sleeve 244 has attachment fixtures 248 for attaching othercomponents, such as arm 128, bridge 160, or actuators 140, 142, 150, or152. Likewise, inner sleeve 246 may have attachment fixtures 250 inaddition to those on the outer sleeve or instead.

Ball screw actuator 242 includes bearings 252 and 254 in the form ofrings disposed between sleeves 244 and 246 to facilitate the relativesliding motion during telescoping, as is common with a hydrauliccylinder. As shown in FIG. 12B, for example, bearing 254 is fixed toinner sleeve 246 and bearing 252 is fixed to outer sleeve 244. Bearing254 moves with sleeve 246 over the surface of sleeve 244 while bearing252 moves with sleeve 244. The bearings 252 and 254 may be made fromultra high molecular weight (UHMW) plastic to provide coefficients offriction for low wear and the load bearing strength to support therequired loads and bending moments that may occur at any angle. Ballscrew actuator 242 may include a ball screw mechanism 256. Ball screwmechanism 256 may be implemented, for example, using a ball screw 257driven by an electric or pneumatic motor 258 through a gear box 260 sothat ball screw 257 pushes or pulls drive sleeve 262, which is fixedrelative to inner sleeve 246, producing telescoping in or out of innersleeve 246 relative to outer sleeve 244.

The foregoing description relates to exemplary embodiments of theinvention. Modifications may be made without departing from the spiritand scope of the invention as set forth in the following claims.

1. A material handling system comprising: an arm that rotates about anA-axis, the arm having a Z₁-axis in fixed relation to the arm andperpendicular to the A-axis, and having a Z₂-axis in fixed relation tothe arm and parallel to the Z₁-axis so that the Z₁-axis and Z₂-axisrotate together about the A-axis; a bridge carried by the arm, thebridge having a Y₁-axis maintained perpendicular to the Z₁-axis and aY₂-axis maintained perpendicular to the Z₂-axis, the bridge also havingan X₁-axis maintained perpendicular to the Y₂-axis, wherein the bridgetranslates relative to the arm along the Z₁-axis and Z₂-axisindependently and the bridge translates relative to the arm along theY₁-axis and Y₂-axis independently; a first gripper and a second gripperfor gripping the material, wherein the first gripper and second gripperare carried by the bridge and translate along the X₁-axis, and wherein:the first gripper and the second gripper are configured to translatealong the Z₁-axis and Z₂-axis differentially to produce rotation of thematerial about a virtual B-axis perpendicular to the Z₁-axis andZ₂-axis; and the first gripper and the second gripper are translatedalong the Y₁-axis and Y₂-axis differentially to produce rotation of thematerial about a virtual C-axis perpendicular to the Y₁-axis andY₂-axis.
 2. The material handling system of claim 1 farther comprising:a mast having a W-axis that is maintained perpendicular to a floor; anda lift truck carriage carried by the mast, wherein the lift truckcarriage supports the arm, provides rotation of the arm about theA-axis, and translates along the W-axis to move the arm and grippersperpendicularly to the floor.
 3. The material handling system of claim 1farther comprising: a car mounted to the bridge so that the cartranslates relative to the bridge along the X₁-axis wherein: the carrotates about an A′-axis parallel to the X₁-axis; and at least one ofthe first gripper and the second gripper is carried by the car.
 4. Thematerial handling system of claim 1 farther comprising: a chassis thatcarries the arm and has an X-axis and a Y-axis parallel to a floorwherein: the chassis is configured to translate in the direction of theX-axis and in the direction of the Y-axis in combination simultaneouslyso that movement is provided across the floor in any chosen direction.5. The material handling system of claim 1 farther comprising: a chassisthat carries the arm and has an X-axis and a Y-axis parallel to a floorwherein: the chassis translates in the direction of the X-axis and inthe direction of the Y-axis in combination simultaneously so thatrotation of the material relative to the floor is provided about aC′-axis that is perpendicular to both the X-axis and the Y-axis.
 6. Thematerial handling system of claim 1 wherein: at least one of the firstgripper and the second gripper is a self-locking gripper that includesan actuator pivot that pushes against the end of a guide slot inresponse to a force tending to open the self-locking gripper.
 7. Thematerial handling system of claim 1 further comprising: a Z₁-actuatorattached to the arm and that provides translation of the first gripperin the direction of the Z₁-axis; and a Z₂-actuator attached to the armand that provides translation of the second gripper in the direction ofthe Z₂-axis independently of the Z₁-actuator.
 8. The material handlingsystem of claim 7 further comprising: a Y₁-actuator attached to theZ₁-actuator and that provides translation of the first gripper in thedirection of the Y₁-axis; and a Y₂-actuator attached to the Z₂-actuatorand that provides translation of the second gripper in the direction ofthe Y₂-axis independently of the Y₁-actuator.
 9. The material handlingsystem of claim 7 wherein: at least one of the Z₁-actuator and theZ₂-actuator includes an inner sleeve that telescopes within an outersleeve and a pair of telescope bearings disposed between the innersleeve and the outer sleeve that support loads placed at any non-zeroangle relative to a longitudinal axis of the inner and outer sleeves.10. A mandrel segment loader comprising: a bridge that translatesrelative to an arm in the directions of a Z₁-axis, a Y₁-axis, a Z₂-axis,and a Y₂-axis all independently of each other, and wherein: the Z₁-axisand the Y₁-axis are perpendicular; the Z₂-axis and the Y₂-axis areperpendicular; the Z₁-axis and the Z₂-axis are parallel and maintainedin fixed relation to each other and the arm; coordinated motion of thebridge in the directions of the Y₁-axis and the Y₂-axis providesrotation of a mandrel segment about a C-axis that is a virtual axisperpendicular to the Y₁-axis and the Y₂-axis; and coordinated motion ofthe bridge in the directions of the Z₁-axis and the Z₂-axis providesrotation of the mandrel segment about a B-axis that is a virtual axisperpendicular to the Z₁-axis and the Z₂-axis; and a self-locking gripperthat translates in the direction of an X₁-axis relative to the bridgeand rotates about an A′-axis relative to the bridge.
 11. The mandrelsegment loader of claim 10 further comprising: an arm that translates inthe direction of a W-axis and rotates about an A-axis; a Z₁-actuatorattached to the arm that provides translation of the bridge in thedirection of the Z₁-axis; and a Z₂-actuator attached to the arm thatprovides translation of the bridge in the direction of the Z₂-axisindependently of the Z₁-actuator, wherein: each of the Z₁-actuator andthe Z₂-actuator comprises a ball screw actuator with an inner sleevethat telescopes within an outer sleeve and a pair of ultra highmolecular weight plastic telescope bearings disposed between the innersleeve and the outer sleeve that support loads placed at any non-zeroangle relative to a longitudinal axis of the inner and outer sleeves.12. The mandrel segment loader of claim 11 further comprising: aY₁-actuator attached to the Z₁-actuator and to the bridge that providestranslation of the bridge in the direction of the Y₁-axis; and aY₂-actuator attached to the Z₂-actuator that provides translation of thebridge in the direction of the Y₂-axis independently of the Y₁-actuator.13. The mandrel segment loader of claim 12 further comprising: a lengthadjustment mechanism wherein: the bridge is attached to the Y₁-actuatorvia the length adjustment mechanism; and the length adjustment mechanismcompensates for changes in distance between the Y₁-actuator andY₂-actuator as the bridge is moved in the directions of the Z₁-axis theZ₂-axis, and any combination of the Z₁-axis and the Z₂-axis.
 14. Themandrel segment loader of claim 11 further comprising: a chassissupported by wheels wherein: the chassis provides motion of the mandrelsegment loader across a floor in the direction of an X-axis and in thedirection of a Y-axis in combination simultaneously so that movement isprovided in any chosen direction across the floor; and the chassisprovides motion of the mandrel segment loader across the floor in thedirection of the X-axis and in the direction of the Y-axis incombination simultaneously so that rotation of the mandrel segmentcentered at any chosen point is provided about a C′-axis that isperpendicular to both the X-axis and the Y-axis; a mast attached to thechassis and providing support for translation of the arm and bridge inthe direction of the W-axis; and a lift truck carriage that slides alongthe mast in the direction of the W-axis, wherein the arm is mounted tothe lift truck carriage so that the arm rotates about the A-axis. 15.The mandrel segment loader of claim 10 further comprising: a carsupported on rollers within guide tracks attached to the bridge and on afirst and second side of the car, wherein: the self-locking gripper isattached to the car; movement of the car along the guide tracks providestranslation in the direction of the X₁-axis of the self-locking gripper;and the height of the car is differentially adjustable as between thefirst side and the second side of the car with respect to the guidetracks by adjusting the rollers about an eccentric so that the carrotates about an A′-axis parallel to the X₁-axis providing A′-axisrotation of the self-locking gripper.
 16. A method of material handlingcomprising the operations of: gripping the material using a firstgripper and a second gripper; carrying the first gripper and secondgripper on a bridge having a Y₁-axis maintained perpendicular to aZ₁-axis and a Y₂-axis maintained perpendicular to a Z₂-axis, the bridgealso having an X₁-axis maintained perpendicular to the Y₂-axis; rotatingthe bridge about an A-axis on an arm, the arm having the Z₁-axis infixed relation to the arm and perpendicular to the A-axis, and havingthe Z₂-axis in fixed relation to the arm and parallel to the Z₁-axis sothat the Z₁-axis and the Z₂-axis rotate together about the A-axis;translating the bridge relative to the arm along the Z₁-axis and Z₂-axisindependently and translating the bridge relative to the arm along theY₁-axis and the Y₂-axis independently; translating the first gripper andthe second gripper together along the X₁-axis; translating the firstgripper and the second gripper along the Z₁-axis and the Z₂-axisdifferentially to produce rotation of the material about a virtualB-axis perpendicular to the Z₁-axis and the Z₂-axis; and translating thefirst gripper and the second gripper along the Y₁-axis and the Y₂-axisdifferentially to produce rotation of the material about a virtualC-axis perpendicular to the Y₁-axis and the Y₂-axis.
 17. The method ofclaim 16 wherein the gripping operation includes: moving an actuator rodin a first direction to transmit force through a thumb control link anda finger control link to close the thumb and finger for engaging a barattached to the material; and transmitting counter force tending to openthe finger and the thumb back through the thumb control link and thefinger control link to push the actuator rod in the first directionclosing the thumb and the finger.
 18. The method of claim 16 furthercomprising the operation of: lifting the arm and material in thedirection of a W-axis perpendicular to a floor.
 19. The method of claim16 further comprising the operation of: transporting the material bymoving the arm in the direction of an X-axis and a Y-axis simultaneouslyand in coordination to produce an overall translation and rotation ofthe material across a floor.